Marine seismology companies invest heavily in the development of marine seismic surveying equipment and seismic data processing techniques in order to obtain accurate, high-resolution seismic images of subterranean formations located beneath a body of water. High-resolution seismic images are used to determine the structure of subterranean formations, discover hydrocarbon deposits, and monitor hydrocarbon deposits during production. A typical marine seismic survey is carried out with a survey vessel that tows one or two seismic sources and a number of streamers below the surface of the body of water. A typical seismic source comprises an array of source elements, such as air guns. The streamers are elongated cable-like structures towed behind the survey vessel in the direction the survey vessel is traveling. Each streamer includes a number of receivers that generate seismic data in response to detecting pressure and/or particle motion wavefields. The streamers are arranged substantially parallel to one another to form a seismic data acquisition system. The survey vessel contains seismic acquisition equipment, such as navigation control, seismic source control, seismic receiver control, and seismic data recording equipment.
A typical marine seismic survey is carried out by activating the one or more seismic sources above a subterranean formation. Each activation produces an acoustic signal that expands outward in all directions. A portion of the acoustic signal travels downward through the body of water and into the subterranean formation. At each interface between different types of rock and sediment, a portion of the acoustic signal is refracted, a portion is transmitted, and another portion is reflected back from each interface into the body of water to propagate toward the free surface. The portion of the acoustic signal reflected back into the body of water and that travels directly to the receivers is called a primary reflected wavefield or simply a primary. Other portions of the acoustic signal that is reflected back into the body of water may be reflected a number of times between the free surface and between interfaces within the subterranean formation before reaching the receivers. These multiple reflected wavefields are called multiples. Multiples are typically treated as noise and are suppressed in seismic imaging. In recent years, multiples have been recognized as containing valuable information about the subterranean formation. As a result, techniques have been developed to generate seismic images from both primaries and multiples. However, the resulting seismic images typically have a low signal-to-noise ratio and are often contaminated with adverse crosstalk effects, which lowers the resolution of the seismic images.